1. Field of the Invention
The present invention relates to a high temperature bearing alloy for use in high temperature oxidizing atmosphere and also to a method of producing the same.
2. Description of the Related Art
Hitherto, materials of a type composed of a base metal such as copper or iron and containing a solid lubricant such as graphite dispersed or embedded therein have been used as materials of bearings which are used in high temperature oxidizing atmosphere These known materials, however, cannot be used satisfactorily at temperatures exceeding 500.degree. C. or so, due to rather inferior heat-resistance exhibited by the base metal and the solid lubricant. In order to cope with demands for higher sliding characteristic, materials have recently been proposed which are produced by dispersing hard particles of Co-Mo-Cr-Si alloy in heat-resistant steels by using powder metallurgical technique Such materials are usable, as disclosed in Japanese Patent Unexamined Publication No. 3-24249, as bearing materials which are required to operate at high temperatures up to 700.degree. C. or so.
In recent years, there is a demand for bearing materials used at still higher temperatures exceeding 700.degree. C., such as the bearings for supporting, for example, exhaust gas control valves used in gasoline or diesel engines, gas control valves used in gas turbines, and so forth. Unfortunately, known bearings could not fully meet such demand because they are safely usable only at temperatures not higher than 700.degree. C.
Attempts have been made to use heat-resistant alloys or ceramics as the bearing materials, but such attempts also are unsuccessful due to high friction coefficients exhibited by such types of materials.